The present invention relates to methods of manufacturing reflective sheeting, with particular application to cube corner retroreflective sheeting.
The reader is directed to the glossary provided at the end of the specification for guidance on the meaning of certain terms used herein.
It is known for manufacturers of high visibility garments, such as vests worn by construction work zone crews, to use laminating machines to bond strips of beaded retroreflective sheeting to a fabric, the composite fabric then being cut, sewn, or otherwise configured to produce the desired garment. The laminating machines in such manufacturing processes utilize a pair of endless belts that support and hold the retroreflective sheeting and fabric as they pass through an extended heated zone. The heat activates an adhesive provided on one side of the retroreflective sheeting. Such machines also pass the components thus heated through a nip formed between two unheated rubber rollers to secure the retroreflective sheeting to the fabric in a lasting bond. In these processes, the integrity of the retroreflective sheeting is undisturbed because the tiny beads responsible for retroreflectivity are unaffected by the temperatures and pressures employed.
U.S. Pat. No. 5,770,124 (Marecki et al.), U.S. Pat. No. 5,814,355 (Shusta et al.), U.S. Pat. No. 5,840,405 (Shusta et al.), and U.S. Pat. No. 5,948,488 (Marecki et al.) (collectively, the xe2x80x9cMarecki et al. patentsxe2x80x9d) disclose a wide variety of methods of manufacturing glittering cube corner sheeting. Both batch and continuous processes are disclosed for converting non-glittering cube corner sheeting, whose cube corner elements are initially well-ordered, into glittering cube corner sheeting. Disclosed processes involve exposing the non-glittering cube corner sheeting to heat, pressure, or a combination thereof.
Sheeting sold in long continuous rolls has certain advantages over sheeting sold in other forms such as individual rectangular sheets. One advantage is better compatibility with automated converting operations in which strips or other pieces of the sheeting are applied to end-use products such as shoes, garments, or the like. In connection with attempting to convert entire rolls of non-glittering cube corner sheeting into corresponding rolls of glittering cube corner sheeting, certain difficulties were encountered when simply feeding the non-glittering cube corner sheeting (together with a textured cloth material in contact with the cube corner elements) into a heated nip using a heated roller or rollers. The high pressures and temperatures required to produce a glittering appearance tended to cause the rubber surface of the roller to break down, and also sometimes resulted in shrinkage or puckering of the sheeting after passing through the nip. Furthermore, only relatively slow process speeds could be achieved.
An improved process for converting a non-glittering cube corner sheeting to a glittering cube-corner sheeting, not subject to the foregoing problems and capable of handling entire rolls of cube corner sheeting, would be highly desirable.
The present invention is a specific improvement or niche within the very broad and generic concepts that are taught and/or claimed in the Marecki et al. patents. I.e., the improvement relates to known processes for imparting a glittering or sparkling appearance to an initially non-glittering cube corner sheeting by exposing the sheeting to heat, pressure, or a combination thereof. Such an improvement as disclosed herein typically includes (1) passing the sheeting through an extended heated zone, (2) applying pressure to the sheeting after it has been heated in the extended heated zone, and (3) supporting the sheeting with at least one belt as the sheeting is passed through the extended heated zone, and as the pressure is applied thereto. The extended heated zone preferably has a length in the downweb direction at least as great as a width of the sheeting. The applied pressure is preferably provided by a pair of rollers that are unheated or at least cooler than temperatures within the extended heated zone. The at least one belt is preferably a pair of endless belts between which the sheeting is supported as it is heated, as the pressure is applied, and further as it is at least partially cooled after application of the pressure.